Câu 3:Một phân tử ADN có khối lượng là 1440000đvc và có số nu loại ađênin là 960nu. a,Tính số lượng và tỉ lệ phần trăm từng loại nu của phân tử ADN b,Tính chiều dài của phân tử ADN

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Điền mạo từ "a,anthe" Exercise 1: Choose the best answer (chú ý: ký hiệu “x” có nghĩa là không cần mạo từ) 1. We are looking for _______ place to spend ________ night. A. the/ the B. a/ the C. a/ a D. the/ a 2. Please turn off ________ lights when you leave ________ room. A. the/ the B. a/ a C. the/ a D. a/ the 3. We are looking for people with ________experience. A. the B. a C. an D. x 4. Would you pass me ________ salt, please? A. a B. the C. an D. x 5. Can you show me ________way to ________station? A. the/ the B. a/ a C. the/ a D. a/ the 6. She has read ________interesting book. A. a B. an C. the D.x 7. You’ll get ________shock if you touch ________ live wire with that screwdriver. A. an/ the B. x/ the C. a/ a D. an/ the 8. Mr. Smith is ________ old customer and ________ honest man. A. An/ the B. the/ an C. an/ an D. the/ the 9. ________ youngest boy has just started going to ________ school. A. a/ x B. x/ the C. an/ x D. the/ x 10. Do you go to ________ prison to visit him? A. the B. a C. x D. an 11. ________eldest boy is at ________ college. A. a/ the B. the/ x C. x/ a D. an/ x 12. Are you going away next week? No, ________ week after next. A. an B. a C. the D. x 13. Would you like to hear ________ story about ________ English scientist? A. an/ the B. the/ the C. a/ the D. a/ an 14. There’ll always be a conflict between ________ old and ________ young. A. the/ the B. an/ a C. an/ the D. the/ a 15. There was ________ collision at ________ corner. A. the/ a B. an/ the C. a/ the D. the/ the 16. My mother thinks that this is ________ expensive shop. A. the B. an C. a D. x 17. Like many women, she loves ________ parties and ________gifts. A. the/ a B. a/ the C. a/ a D. x/ x 18. She works seven days ________ week. A. a B. the C. an D. x 19. My mother goes to work in ________ morning. A. a B. x C. the D. an 20. I am on night duty. When you go to ________ bed, I go to ________ work. A. a/ x B. a/ the C. the/ x D. x/ x Exercise 2: Complete with a, an, the or x 1. There was ________knock on ________door. I opened it and found ________small dark man in ________blue overcoat and _______woolen cap. 2. He said he was ________employee of ________gas company and had come to read ________meter. 3. But I had ________suspicion that he wasn't speaking ________truth because ________meter readers usually wear ________peaked caps. 4. However, I took him to _______ meter, which is in _______dark corner under _______ stairs. 5. I asked if he had ________ torch; he said he disliked torches and always read ________ meters by ________light of ________match. 6. To prevent ________possible repetition of this accident, I lent him ________torch. 7. He said that he had had ________book but that it had been burnt in ________fire in________ Mr. Smith's house. 8. By this time I had come to ________conclusion that he wasn't ________genuine meter reader; and ________moment he left ________house I rang ________police. 9. I can't remember ________exact date of ________storm, but I know it was on ________Sunday because everybody was at ________church. On ________Monday ________post didn't come because ________roads were blocked by ________fallen trees. 10. Professor Jones, ________man who discovered ________new drug that everyone is talking about, refused to give ________press conference.